We've seen this with POP clients on workstations that run anti-virus
software. Ex. Symantec with 'Internet Email Auto-Protect' enabled.

The anti-virus filter 'intercepts' the message while it is downloading
so that the POP client never signals the mail server that the download
completed successfully.  Thus the same message is downloaded again with
subsequent connections.

Janet Shih
Messaging and Server Infrastructure
Information Technology Services
Louisiana State University


>-----Original Message-----
>From: LISTSERV site administrators' forum [mailto:LSTSRV-
>[log in to unmask]] On Behalf Of Bill Verity
>Sent: Thursday, April 02, 2009 10:13 AM
>To: [log in to unmask]
>Subject: Problem with duplicate listserv mail in Outlook
>
>We have had a long standing problem with people using Outlook.  Doesn't
>happen very often -- just enough to be a nuisance.  Problem looks like
>this:
>
>User has Outlook set to leave mail on server because they want to check
>mail from several computers.
>Some mail from listserv is downloaded, but for some reason outlook
doesn't
>remember.
>Next time mail is checked. another copy is downloaded.
>This continues until either the client unchecks leave mail on server or
the
>mail is removed from the server by some other technique.
>
>Have others seen this problem?  I thought I had seen it discussed, but
I
>can't find anything in the archives.  I got some hits from Microsoft
for
>Outlook 2002, but nothing newer.
>--
>Bill Verity - 814-865-4758  Fax: 814-863-7049
>Listserv Administrator
>204S Wagner Building - Information Technology Services, Penn State
>University
>At the office - on my Mac, of course ;-)